Centrifugal blowers for use in HVAC systems are known in the art. A centrifugal blower is used to impart motion to a gas stream flowing therethrough. A centrifugal blower generally includes an impeller having blades formed on a circumference thereof and a scroll housing surrounding the impeller. A gas enters the centrifugal blower axially through an inlet while rotation of the impeller causes the gas to be directed outwards due to the effects of centrifugal force, causing suction within the center of the impeller. As the gas is directed toward the exterior of the centrifugal blower, the scroll housing directs the gas around the periphery of the centrifugal blower until it exits the centrifugal blower at an outlet.
One potential problem associated with traditional centrifugal blowers is that there is typically an uneven distribution of pressure across the blades of the impeller as the blades extend away from an inlet of the blower. This occurs due to a change in direction of the gas flow as it enters the blower axially before being turned about 90° as it is directed outwards by the rotation of the impeller. The blades of the impeller typically include a linear surface adjacent a central hub of the impeller with the linear surface of the blades arranged in parallel to an axis of rotation of the impeller, as disclosed in U.S. Patent Application Publication No. 2013/0209245 to Iyer et al., which is hereby incorporated herein by reference in its entirety. Gas flowing into the centrifugal blower axially must turn as it enters the space between adjacent blades and is directed outwards. Gas flowing through a central region of the inlet is allowed to turn gradually as it turns towards the blades while air entering the peripheral regions of the inlet must turn much more sharply to enter the spaces between the blades adjacent the inlet of the blower. As a result, the portions of the blades adjacent the inlet of the blower tend to experience a lower gas flow therethrough, negatively affecting the efficiency of the blower. Furthermore, the gas that does flow through the portions of the blades adjacent the inlet tends to experience a greater pressure loss due to turning losses associated with the sharp turn experienced by the gas flow.
Furthermore, traditional blowers tend to experience a large difference in static pressure at different regions within the scroll housing. For instance, the static pressure formed around the periphery of the impeller may be highest adjacent the outlet of the blower. In blowers having impeller blades that do not have an equal distribution of pressure along a length of each blade, there can be situations where the high pressure gas adjacent the outlet will backflow into the low pressure regions of the impeller blades. The backflow into the blades can cause rumble noise to be generated that can propagate through the HVAC system and be heard by a passenger in a vehicle, for example, having the blower installed therein.
It would therefore be desirable to produce a centrifugal blower having a maximized efficiency by providing an even distribution of pressure across the blades of the impeller and minimizing a turning angle of a gas flowing through the centrifugal blower before it strikes a leading edge of each of the blades of the impeller.